Last summer, when Mae Tingstrom had the idea to open a romance bookstore in Ventura, Calif., the first thing she did was search online to see whether there was already one in her region. She found The Ripped Bodice — a bookstore in Culver City that was doing so well, it was expanding to a second location in Brooklyn.

“That was intimidating,” she said.

If their success was daunting, it also suggested that there might be room for another romance store. So this February, she opened Smitten on a busy strip of Main Street, about 60 miles from her competitor. In the months since, Smitten has become a vibrant hub for romance readers, with author signings, tarot readings, book clubs and trivia and craft nights.

Customers sometimes approach her with highly specific requests. “Someone came in and was like, ‘I like fantasy, I want it to be queer, I want it to have representation from a different culture and I want it to be as smutty as possible,’” Tingstrom said.

And they come in often. “I have regulars who come a couple of times a week,” Tingstrom said. “I’m like, didn’t you just buy two books the other day?”

Once a niche that independent booksellers largely ignored, romance is now the hottest thing in the book world. It is, by far, the top-selling fiction genre, and its success is reshaping not only the publishing industry, but the retail landscape as well.